Diagnosis of associated injuries depends on a complete history and physical exam of the involved extremity. If any hard signs of vascular injury are present, then consult vascular surgery immediately. If there are any soft signs of vascular injury and/or if the ankle-brachial index is <0.9, then order imaging tests to evaluate for associated vascular injuries, or transfer to an institution with vascular care capability (Figure 266-1).
Algorithm for penetrating extremity trauma. ABI = ankle-brachial index.
The differential diagnosis for injuries associated with penetrating trauma to the extremities includes arterial or venous injury, nerve damage, tendon lacerations, fractures, soft tissue injury, degloving injuries, damage to joint capsule, bullet embolization of artery, or vein and compartment syndrome.11
No specific laboratory testing is indicated for isolated penetrating extremity injuries; in certain cases, type and screening and a CBC may be indicated. If the patient has soft signs of vascular injury or an ankle-brachial index <0.9, then obtain a creatinine to determine renal function in patients with risk for preexisting renal disease. Underlying renal insufficiency creates potential for contrast-induced nephropathy when performing CT angiography. See chapter 88, "Acute Kidney Injury" for discussion of radiocontrast-induced nephropathy.
Obtain anteroposterior and lateral radiographs of extremities with suspected fracture, joint injury, or retained bullet or other foreign body fragments. Oblique views may add value if the physician has a strong clinical suspicion of retained foreign body and it is not shown on anteroposterior and lateral views. Obtain radiographs of the joint above and below the site of injury. Evidence of air in the joint or an intra-articular fracture on the radiograph demonstrates that joint involvement has occurred.
There are four types of fracture patterns associated with low-energy gunshots12 (Figure 266-2). The drill-hole wound track pattern appears in the more porous and lower density cancellous bone. This pattern is most common in the distal femur, pelvis, and proximal humerus. Unicortical fractures appear in the metaphyses of long bones and occur only due to tangential impact with the bone. Comminuted fractures occur most frequently in diaphyseal bone; multiple bone fragments are common. The fourth type of fracture is the distal spiral fracture, and this occurs most commonly in the femur. There is controversy in the literature over whether this fracture is caused by the bullet itself or associated with falls that occur after the gunshot injury is sustained.13
Fracture patterns created by bullets: drill-hole (A), unicortical (B), distant spiral (C), comminuted (D).
For shotgun or blast injuries, obtain radiographs of the extremity and joint distal to the injury in order to detect any pellets that have embedded into the bone, remain in the soft tissues, or have potentially entered into a joint capsule (Figure 266-3).
A. Gunshot wound to the shoulder and axilla. B. Embedded pellet of shotgun in the distal ulna, illustrating the importance of obtaining images of the extremity distal to such injuries.
CT angiography is the primary diagnostic study for the evaluation of vascular injuries to the extremities.2 CT angiography is noninvasive, provides higher resolution images, and is less expensive when compared to catheter angiography. It provides three-dimensional reconstruction with minimal artifact. CT angiography also assists in the evaluation of extravascular injuries such as fractures, foreign objects, or joint involvement.14 Studies comparing CT angiography to catheter angiography have demonstrated that the CT angiography sensitivity and specificity rates for identifying clinically significant arterial injuries are equivalent to those with conventional catheter angiography.15,16,17,18 Limitations of CT angiography include scatter artifact interference caused by bullets, poor visualization of tibial vessels, and the inability to perform any therapeutic interventions during the study.
Color flow duplex ultrasonography has a sensitivity that ranges from 50% to 100% for evaluating vascular injuries.19,20 Given this mixed evidence of accuracy, color flow duplex ultrasonography should not be used as the primary diagnostic study to rule out vascular injuries associated with penetrating trauma to extremities.10